JP4112884B2 - Superconducting material - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a current limiting element, a current limiting fuse, a current lead, a permanent current switch, and a superconducting member in which a plurality of wires are connected using an oxide superconducting thin film.
[0002]
[Prior art]
Since oxide superconductors such as Y-based and Bi-based materials can use inexpensive liquid nitrogen as a refrigerant, development aimed at power applications such as superconducting cables and current limiters is being actively promoted. Among them, since the oxide superconducting thin film provided on the oxide single crystal base material having a lattice constant close to that of the oxide superconductor has a single crystal orientation, 10⁶A / cm²It has the characteristic of having a high critical current density of the order. As a result, the film thickness necessary for obtaining a high critical current can be reduced, and the generated resistance per unit length when transitioning to the normal conducting state can be increased. Therefore, in recent years, the oxide superconducting thin film provided on the oxide single crystal substrate suppresses the electric power system accident current by utilizing the rapid increase in resistance, ie, the transition from the superconducting state to the normal conducting state (quenching). Applications to current control superconducting elements such as current limiting elements are attracting attention.
[0003]
By the way, since the rated capacity of the power system is large, in a current-limiting element at a practical level, 3-5 m²It is assumed that a superconducting thin film having a large area is used. However, at present, the size of one superconducting thin film is limited to about 10 to 20 cmφ depending on the size of the oxide substrate and the size of the film forming apparatus for producing the superconducting thin film. Therefore, it is necessary to connect a large number of superconducting thin films in series and in parallel. At the time of such connection, it is important that the superconducting characteristics are not deteriorated by the connection. Further, in order to reduce the loss during normal energization, it is required that the resistance generated by the connection is small. In addition, it is important that there is no deterioration of the connection due to the thermal cycle because it is repeatedly heated by Joule heat at the time of quenching and then repeatedly cooled to liquid nitrogen temperature when returning to the superconducting state. is there.
[0004]
[Problems to be solved by the invention]
Conventionally, PbSn alloy solder has been mainly used to connect metallic superconducting wires, Bi-based Ag sheathed wires, Y-based and Bi-based bulk superconductors. However, when PbSn alloy solder is applied to the connection between the oxide superconducting thin film on the oxide substrate and the wire, it reacts with a noble metal electrode such as Ag or Au provided on the oxide superconducting thin film, and the superconducting properties There was a difficulty of deteriorating. Moreover, Pb is harmful and is not preferable from the viewpoint of environmental protection. In this specification, “solder” is used as a general term for low-melting-point metals that can be electrically connected by reacting with a part of a material to be connected by heating and melting.
[0005]
In addition, it has been attempted to press-bond In to an Ag electrode on an oxide superconducting thin film (Japanese Patent Laid-Open No. 11-204845) or connect a lead to an Ag electrode of an oxide superconducting thin film using In as solder. (Japanese Patent Laid-Open No. 5-251761).
[0006]
However, when the present inventors further tried the method of pressure-bonding In to the Ag electrode on the oxide superconducting thin film, there was a problem that connection peeling was often observed and the connection resistance was increased.
[0007]
In addition, when the present inventors re-examined the method of using In as solder, that is, by melting In and connecting the Ag electrode on the oxide superconducting thin film and the metal wire, the connection resistance is large or the superconducting characteristics deteriorate. In some cases, the superconducting properties deteriorate with the passage of time. This is presumably because In reacted with the Ag electrode and further diffused and reacted to the oxide superconducting thin film. In other words, since In is easily oxidized, oxygen in the oxide superconducting thin film is stripped and a part of the oxide superconducting thin film is converted to a non-superconductor, resulting in degradation of superconducting properties and increased connection resistance. Is done.
[0008]
In addition, when the inventors tried to connect the Au electrode on the oxide superconducting thin film to a metal wire using In as solder, the superconducting property was not observed to be deteriorated, but the connection resistance was large or the thermal cycle was reduced. There was a problem that the connection resistance would increase after repeating. This is presumed that the connection resistance was increased because the wettability of In with Au was poor and good connection was difficult to obtain.
[0009]
The purpose of the present invention is to prevent deterioration of superconducting properties and connection due to thermal cycling in a superconducting member in which an oxide superconducting thin film provided on an oxide substrate and a metal wire or an oxide superconducting wire are connected. In addition, it is to realize a low connection resistance.
[0010]
[Means for Solving the Problems]
  A superconducting member according to an aspect of the present invention includes an oxide superconducting thin film provided on an oxide base; an electrode including Au, Ag, or an AgAu alloy provided on the oxide superconducting thin film; A metal wire or an oxide superconducting wire to be connected to the superconducting thin film; an InAg alloy having an additive amount of Ag of 0.5 wt% to 10 wt% connecting between the electrode and the wireConsist ofWith solder.
[0011]
  A superconducting member according to another aspect of the present invention includes an oxide superconducting thin film provided on an oxide substrate; an electrode provided on the oxide superconducting thin film and having an Au layer and an Ag layer laminated; A metal wire or oxide superconducting wire connected to the oxide superconducting thin film; and an In or InAg alloy connecting between the electrode and the wireConsist ofWith solder.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
  Embodiments of the present invention will be described below.
  A superconducting member according to an embodiment of the present invention is formed by forming an electrode containing Au, Ag or an AgAu alloy on an oxide superconducting thin film provided on an oxide substrate, and the electrode and a metal wire or an oxide superconducting material. InAg alloy in which the addition amount of Ag is 0.5 wt% to 10 wt%Consist ofIt is connected with solder.
[0013]
When an electrode containing a noble metal such as Au, Ag or an AgAu alloy is formed on the oxide superconducting thin film, the contact resistance between the oxide superconducting thin film and the noble metal electrode is small, so that the connection resistance can be reduced when connected to a metal wire or the like. .
[0014]
Here, when an InAg alloy is used as a solder for connecting an Ag electrode to a metal wire or the like, since Ag is added to the solder in advance, there is little reaction with the electrode, and In directly reacts with the oxide superconducting thin film. Can be prevented. For this reason, deterioration of superconducting characteristics can be prevented. Further, since a non-superconducting layer is not generated at the interface between the electrode and the oxide superconducting thin film, the connection resistance can be reduced.
[0015]
In order to suppress the reaction between In and the Ag electrode as described above, the amount of Ag added in the InAg alloy used as solder is set to at least 0.5 wt% or more. On the other hand, when the amount of Ag added to the InAg alloy exceeds 10% by weight, the connection resistance increases. This is presumed to be due to the following reason. That is, when the added amount of Ag in the InAg alloy is 3% by weight or more, the melting point tends to gradually increase with the added amount. For this reason, in an InAg alloy with a high Ag addition amount, In reacts with oxygen in the air at a high temperature at the time of melting, a high resistance body such as indium oxide is generated, and as a result, the connection resistance is estimated to increase. . Accordingly, the amount of Ag added to the InAg alloy is preferably 0.5% by weight to 10% by weight, and more preferably 1% by weight to 5% by weight.
[0016]
Further, it has been found that when an InAg alloy is used as a solder for connecting an Au electrode to a metal wire or the like, the connection resistance is reduced as compared with the case where In is used. This is presumably because the InAg alloy has higher wettability to the Au electrode than In, and a good connection was obtained.
[0017]
In the above description, the case where the InAg alloy is used for the solder has been described as an example. However, in order to obtain the same effect as described above even when the SnAg alloy is used for the solder, the Ag addition amount is 0.5 wt. % To 10% by weight is preferable, and 1% to 5% by weight is more preferable.
[0018]
  In a superconducting member according to another embodiment of the present invention, an electrode in which an Au layer and an Ag layer are stacked is formed on an oxide superconducting thin film provided on an oxide substrate, and the electrode and a metal wire or an oxidation material are formed. Superconducting wire with In or InAg alloyConsist ofIt is connected with solder. In or InAg alloy used as solder has a property that it easily reacts with Ag and hardly reacts with Au.
[0019]
  It has been found that when an electrode in which an Au layer and an Ag layer are stacked as in this embodiment is used, the connection resistance can be reduced by an order of magnitude compared to an electrode having only an Au layer without an Ag layer. This is because the Ag layer was providedInThis is presumably because the wettability was improved and a good connection was obtained. In addition, no deterioration of superconducting properties was observed after connection. This is because Au compared to AgInThis is presumably because the Au electrode worked as a barrier against the diffusion of solder to the oxide superconducting thin film. Here, in the thin film growth of Au, it is known that island-like growth occurs when the film thickness is small, and islands are connected and become layered when the film thickness is thick. Therefore, in order for the Au layer to function as a barrier, the thickness of the Au layer is preferably 50 nm or more, which has shifted to layer growth. On the other hand, the upper limit of the film thickness of the Au layer is preferably 10 μm or less in order to suppress peeling due to the difference in thermal expansion coefficient between Au, the oxide superconducting thin film, and the oxide base material. A more preferable range of the thickness of the Au layer is 100 nm to 1 μm.
[0020]
In order to improve the wettability of the solder, the Ag layer preferably has a thickness of at least 500 nm. On the other hand, if the Ag layer becomes too thick, the Ag layer itself tends to peel off. A more preferable range of the thickness of the Ag layer is 1 μm to 10 μm.
[0021]
The oxide superconductor used in the embodiment of the present invention is not particularly limited, and examples thereof include oxide superconductors represented by the following general formula.
[0022]
La_2-xAE_xCuO_Four(Wherein AE is at least one element selected from the group consisting of Ba, Sr and Ca, and x is a number satisfying 0.02 ≦ x ≦ 0.08)
REBa₂Cu_ThreeO_{7- δ}(Wherein RE is at least one element selected from rare earth elements such as Y, Sc, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, and δ is oxygen deficient. And is usually a number of 1 or less)
Bi₂Sr₂Ca₁Cu₂O_{8 + d}
Bi₂Sr₂Ca₂Cu_ThreeO_{10 + d}
Bi₂Sr₂Ca_ThreeCu4O_{12 + d}
Tl₂Ba₂Ca₁Cu₂O_{7 + d}
Tl₂Ba₂Ca₂Cu_ThreeO_{10 + d}
Tl₂Ba₂Ca₂Cu_ThreeO_{9 + d}
(In each of the above formulas, d represents a slight variation in oxygen deficiency. Note that part of Bi and Tl can be replaced with Pb, and part of Sr, Ca, and Ba can be replaced with RE elements).
[0023]
In the embodiment of the present invention, as a method for forming a superconducting thin film, for example, various thin films and thick film forming methods such as vapor deposition, sputtering, laser vapor deposition, CVD, MOD, and LPE can be applied. is there. In the embodiment of the present invention, various thin film forming methods such as a vapor deposition method, a sputtering method, and a thermal spraying method can be applied as a method for forming a noble metal electrode such as Ag or Au. In order to reduce the contact resistance between the noble metal electrode and the superconducting thin film, it is preferable to continuously produce the electrode without exposure to the air after the superconducting thin film is formed. When the superconducting thin film is formed and taken out from the film forming apparatus and exposed to the air, carbon dioxide gas, moisture, etc. may adhere to the surface of the superconducting thin film and the superconducting properties near the surface may deteriorate. If an electrode is fabricated on a surface to which carbon dioxide gas or moisture adheres, the contact resistance between the electrode and the superconducting thin film may increase, or the superconducting characteristics may be significantly degraded. In order to remove such carbon dioxide gas and moisture, it is effective to perform a heat treatment in an oxygen atmosphere immediately before the production of the electrode. The heat treatment temperature is preferably in the range of 200 ° C. to 600 ° C., more preferably 400 ° C. to 550 ° C. The heat treatment may be performed in an electric furnace or may be performed in a film forming apparatus for electrode preparation. In order to supplement the oxygen content of the superconducting thin film, it is preferable to use oxygen as the atmosphere gas for the heat treatment, but the effect of removing carbon dioxide gas, moisture and the like can be obtained even in vacuum. Furthermore, it is effective to reduce the contact resistance by performing heat treatment in an oxygen atmosphere after the electrode is manufactured. The temperature of this heat treatment is preferably in the range of 350 ° C. to 600 ° C., more preferably 400 ° C. to 550 ° C.
[0024]
In the embodiment of the present invention, a general method using a soldering iron can be used as a soldering method. In addition, when a temperature-controlled hot plate or the like is applied and soldered, a wide area can be uniformly connected. In addition, the solder layer can be thinned by applying pressure to the connecting portion with a jig or the like when connecting. The solder layer is preferably as thin as possible in order to reduce the connection resistance, and the thickness is preferably 300 μm or less, and more preferably 100 μm or less. The solder layer also has a thickness of at least 10 μm because it also serves to relieve strain due to the difference in thermal expansion coefficient between the oxide superconducting thin film and the oxide substrate and the metal wire or oxide superconducting wire. In order to suppress In oxidation during the connection, the connection is preferably performed in a non-oxidizing atmosphere such as a nitrogen atmosphere, and may be performed in a glove box. Note that trace amounts of elements such as Bi, Cu, and Sb may be added to the InAg alloy or SnAg alloy solder used in the embodiment of the present invention in order to reduce the melting point. Further, the area of the noble metal electrode is preferably larger than the area of the connection surface so that the solder does not directly touch the superconducting thin film. In consideration of solder exudation, the area of the noble metal electrode is preferably large with a width of 10 μm or more around the connection surface. There is no particular upper limit to the size of the electrode, but it is preferable not to increase the electrode unnecessarily in order to increase the resistance generated by the superconducting element during quenching.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0026]
[Example 1]
FIG. 1 is a perspective view of a superconducting member according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a connecting portion of the superconducting member shown in FIG. First, 10 mm width × 120 mm length × 1 mm thickness sapphire is prepared as the oxide base material 1, and CeO is used by laser vapor deposition.₂After forming the buffer layer with a thickness of about 40 nm, YBa₂Cu_ThreeO_{7- δ}An oxide superconducting thin film 2 represented by the following formula was formed to a thickness of about 300 nm. In addition, since it is necessary to hold | maintain a sapphire base material with a holder, the superconducting thin film is not grown in the area | region of 0.5 mm from the base-material edge part. Thereafter, an Ag electrode 3 having a thickness of 2 μm was formed by sputtering on both ends 10 mm × 10 mm in the longitudinal direction using a metal mask, and heat treatment was performed in an oxygen atmosphere using an electric furnace. Next, this superconducting thin film is heated to 140 to 220 ° C., and the InAg solder particles and the current lead 5 are placed on the Ag electrode portion. After the solder is melted, pressure is applied on the current lead 5 by placing a weight on it. In this state, the solder 4 was solidified by cooling.
[0027]
In this example, any one of three types of InAg solders with an Ag addition amount of 0.5 wt%, 3 wt%, or 10 wt% was used. Further, in order to measure only the resistance of the connection portion, a Bi-based Ag sheath wire that shows a superconducting state in liquid nitrogen was used as the current lead 5. The size of the Bi-based Ag sheath wire on the connection surface was 5 mm wide × 8 mm long, and the size of the Ag electrode was 10 mm × 10 mm, which was larger than the former dimension. By observing the connection state using an optical microscope, it was confirmed that the solder was exuded from the connection surface but was smaller than the size of the Ag electrode.
[0028]
The obtained superconducting member was cooled with liquid nitrogen, and the critical current density and the connection resistance were measured by a four-terminal method. In addition, in order to investigate the influence of the thermal cycle, a repeated test was performed in which the temperature was raised to room temperature after the measurement and the measurement was again performed by cooling with liquid nitrogen. Furthermore, the influence of current limiting operation was investigated by energizing a large current to quench the oxide superconducting thin film. As a result, the critical current density is 2 × 10.⁶A / cm²~ 3x10⁶A / cm²Connection resistance is 2 × 10^-8Ωcm²~ 8x10^-8Ωcm²It was confirmed that the critical current density and the connection resistance did not change after the repeated test and the current limiting operation.
[0029]
Further, as described in Comparative Example 1 described later, in the case of PbSn solder, an increase in connection resistance was observed after the repeated test, but in this example, an increase in connection resistance was not observed after the repeated test. This is presumed that InAg is soft even at the temperature of liquid nitrogen, and thus plays a role of relaxing strain due to the difference in thermal expansion coefficient between the oxide and the Bi-based Ag sheath wire. It was found that the connection resistance was the lowest when an InAg alloy with an Ag addition amount of 3 wt% was used. Further, the same measurement was performed one month later, and it was confirmed that there was no change with time in the values of critical current density and connection resistance.
[0030]
  [Reference example 2]
  In the same manner as in Example 1, an Ag electrode formed on an oxide superconducting thin film and a Bi-based Ag sheath wire are added as solder with an Ag addition amount of 0.5 wt%, 3 wt%, or 10 wt% 3 Connection was made using any of the various SnAg alloys. Upon connection, the sample was heated to 220-300 ° C.
[0031]
The obtained superconducting member was cooled in liquid nitrogen and the critical current density and connection resistance were evaluated. As a result, the critical current density was 1.5 × 10⁶A / cm²~ 2x10⁶A / cm²Connection resistance is 5 × 10^-8Ωcm²~ 15 × 10^-8Ωcm²A good value was shown. In this example, the critical current density was lower than that in the case of using the InAg alloy as in Example 1. This is presumably because the melting point of the SnAg alloy is 220 to 300 ° C., which is higher than the melting point of the InAg alloy, 140 to 200 ° C., so that oxygen in the superconducting thin film is easily released and the critical temperature is lowered.
[0032]
[Example 3]
In this example, as shown in FIG. 3, YBa produced on an oxide base material on an alloy was used.₂Cu_ThreeO_{7- δ}The oxide superconducting thin film wires represented by First, a 1 μm-thick CeO film is formed on a Ni alloy having a thickness of about 100 μm by vapor deposition.₂On the base material 8 provided with the oxide layer, YBa having a thickness of 1 μm is formed by laser vapor deposition.₂Cu_ThreeO_{7- δ}An oxide superconducting thin film 2 represented by CeO₂The oxide layer plays a role of preventing a reaction between the Ni alloy and the oxide superconductor, and relaxing a difference in lattice constant between the Ni alloy and the oxide superconductor. Next, a 10 μm thick Ag layer 7 was formed by sputtering to cover the entire surface of the oxide superconducting thin film to form an oxide superconducting thin film wire. Two oxide superconducting wires were produced by the same manufacturing method. Then, as shown in FIG. 3, the Ag layers 7 of the respective wires were faced to each other and heated to 160 ° C., and were connected using an InAg alloy as the solder 4.
[0033]
When the obtained superconducting member was cooled in liquid nitrogen and the connection resistance and critical current density of the connection part were measured by the four-terminal method, the connection resistance was 5 × 10^-8Acm²The critical current density is 1 × 10⁶A / cm²And showed a large value. Also, there was no change in connection resistance and critical current density after repeated thermal cycling.
[0034]
  [Example 4]
  FIG. 4 is a perspective view of a superconducting member according to another embodiment of the present invention, and FIG. 5 is a cross-sectional view of the connecting portion of the superconducting member shown in FIG. As in Example 1, sapphire was used as the oxide substrate 1, and CeO having a thickness of about 40 nm was formed by laser vapor deposition.₂Buffer layer and about 300 nm thick YBa₂Cu_ThreeO_{7- δ}Superconducting thin film 2 was sequentially formed. Next, after cooling the substrate temperature to room temperature, an Au film having a thickness of about 300 nm was formed on the entire surface of the superconducting thin film by vapor deposition without being exposed to the air. Photoresist is formed on this Au film and patterned, and only electrodes 10 mm × 10 mm at both ends in the longitudinal direction are used as electrodes.Au layer 6Then, Au in other regions was etched. Next, an Ag layer 7 having a thickness of about 2 μm was formed on the Au layer 6 by sputtering. thisAg layer 7Area is 8mm x 9mmAu layer 6A little smaller. This superconducting thin film 2 is heated to 160 ° C.Ag layer 7An In or InAg solder grain and a Bi-based Ag sheath wire to be the current lead 5 were placed on top of each other, and after the solder was melted, a weight was placed and pressure was applied. In this state, the solder 4 was solidified by cooling.
[0035]
In this example, any one of four types of solders, pure In with an Ag addition amount of 0 wt%, or an InAg alloy with an Ag addition amount of 0.5 wt%, 3 wt%, or 10 wt% is used. Using. The thickness of the solder 4 was about 50 μm.
[0036]
The obtained superconducting member was cooled with liquid nitrogen, and the critical current density and connection resistance were measured by a four-terminal method. In addition, a repetitive test in which the temperature was raised to room temperature after the measurement and the measurement was again performed by cooling to the liquid nitrogen temperature and a current-limiting test in which a large current was applied to quench the current were performed. As a result, the critical current density is 2 × 10.⁶A / cm²~ 3x10⁶A / cm²It was confirmed that there was no change after repeated tests and current limiting tests, and no change after one month.
[0037]
Regarding the connection resistance, the following results were obtained. When a solder with an Ag addition amount of 0% by weight, that is, pure In (purity 99.99%) is used, the connection resistance is 2 × 10, although it is smaller than the case where there is no Ag layer shown in Comparative Example 3 described later.^-7Ωcm²It was a slightly large value. On the other hand, when an InAg alloy solder with an Ag addition amount of 0.5 wt% to 10 wt% is used, the connection resistance is 2 × 10^-8Ωcm²~ 5x10^-8Ωcm²A good value was shown. Further, it was confirmed that the connection resistance value did not change even after the repeated test or the current limiting test and that there was no change with time even if the same measurement was performed one month later.
[0038]
  [Reference Example 5]
  The oxide superconducting thin film 2 was prepared by the same method as in Example 3, and an electrode in which an Au layer 6 having a thickness of about 300 nm and an Ag layer 7 having a thickness of about 2 μm were stacked was provided and connected using Sn or SnAg alloy solder. . In this example, either one of four types of solders, pure Sn with an Ag addition amount of 0 wt%, or SnAg alloy with an Ag addition amount of 0.5 wt%, 3 wt%, or 10 wt% is used. Using.
[0039]
The obtained superconducting member was cooled with liquid nitrogen, and the critical current density and connection resistance were measured by a four-terminal method. Critical current density is 1.5 × 10⁶A / cm²~ 2x10⁶A / cm²The value was shown. When a solder with an Ag addition amount of 0 wt%, that is, pure Sn (purity 99.99%) is used, the connection resistance is 4 × 10^-7Ωcm²It was a slightly large value. When SnAg alloy solder having an Ag addition amount of 0.5 wt% to 10 wt% is used, the connection resistance is 5 × 10 5.^-8Ωcm²~ 1.5 × 10^-7Ωcm²The value was shown.
[0040]
[Comparative Example 1]
An Ag electrode having a thickness of about 2 μm on the oxide superconducting thin film manufactured by the same method as in Example 1 and a Bi-based Ag sheath wire were connected using PbSn solder. When this superconducting member was cooled in liquid nitrogen and an attempt was made to measure the critical current density, it was found that the superconducting member was not in a superconducting state. This is presumably because Pb reacted with the Ag electrode, diffused to the superconducting thin film and reacted to form a non-superconducting layer. Therefore, the thickness of the Ag electrode was increased to about 10 μm, but the critical current density after connection was 10 μm.^ThreeA / cm²It was a small value with a table. Moreover, when the cooling in liquid nitrogen and the temperature increase to room temperature were repeatedly performed, the connection resistance increased and there was a part that peeled off partly. This is presumably because the thermal strain could not be relieved because the PbSn alloy was hard.
[0041]
[Comparative Example 2]
A 2 μm-thick Ag electrode on the oxide superconducting thin film produced by the same method as in Example 1 and a Bi-based Ag sheath wire were connected using In (purity 99.99%) as solder. The heating temperature at the time of connection was 160 ° C., and five samples were produced under the same conditions. Next, when these samples were cooled in liquid nitrogen and the critical current density and connection resistance were measured, the critical current density was 1 × 10.^FourA / cm²~ 2x10^FourA / cm²A low value and a connection resistance of 5 × 10^-7Ωcm²~ 1x10^-6Ωcm²And showed a large value. It is presumed that this is caused by the reaction of In with Ag as the electrode material and the diffusion of In into the superconducting thin film. Since In is easily oxidized, the oxygen in the superconductor is stripped and a non-superconducting layer is generated, and as a result, it is presumed that the critical current density is lowered.
[0042]
Therefore, five samples with a thick Ag electrode of 10 μm were prepared and the same measurement was performed. As a result, the three samples have a critical current density of 1 × 10⁶A / cm²The above values were shown, but two samples were 10^Four-10^FiveA / cm²And showed a low value. The connection resistance is 5 × 10^-8Ωcm²~ 1x10^-6Ωcm²And the variation was large. Furthermore, when the same measurement was performed one month later, the critical current density was reduced.
[0043]
[Comparative Example 3]
An Au electrode having a thickness of about 300 nm provided on a superconducting thin film manufactured by the same method as in Example 3 and a Bi-based Ag sheath wire were connected using In as solder. Five samples were produced under the same conditions. When these samples were cooled in liquid nitrogen and the critical current density and connection resistance were measured, the critical current density was 2 × 10.⁶A / cm²~ 3x10⁶A / cm²The connection resistance was 1 × 10^-7Ωcm²~ 1x10^-6Ωcm²And showed a large value. Moreover, after repeating the thermal cycle to liquid nitrogen temperature and room temperature, when the same measurement was performed, it turned out that there is no change in critical current density, but connection resistance becomes large.
[0044]
In the above examples, the case where a Bi-based Ag sheath wire is connected to an oxide superconducting thin film in order to measure only the connection resistance has been mainly described as an example, but the film was formed on an alloy substrate. The same effect can be obtained when a superconducting thin film wire is connected or when a general metal wire such as a Cu alloy or an Ag alloy is connected. Further, it goes without saying that the same effect can be obtained in the same type of connection such as between the oxide superconducting thin films, between the oxide superconducting wires provided on the alloy substrate, and between Bi-based Ag sheathed wires.
[0045]
【The invention's effect】
As described above in detail, according to the present invention, in a superconducting member in which an oxide superconducting thin film provided on an oxide substrate is connected to a metal wire or an oxide superconducting wire, connection due to deterioration of superconducting characteristics or thermal cycle Can be prevented, and a low connection resistance can be realized.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a superconducting member of Example 1. FIG.
2 is a cross-sectional view of the superconducting member of FIG.
3 is a perspective view showing a superconducting member of Example 3. FIG.
4 is a perspective view showing a superconducting member of Example 4. FIG.
FIG. 5 is a cross-sectional view of the superconducting member of FIG.
[Explanation of symbols]
1 ... Oxide base material
2 ... Superconducting oxide thin film
3 ... Ag electrode
4 ... Solder
5 ... Electrode lead
6 ... Au layer
7 ... Ag layer
8 ... Base material (Ni alloy / CeO₂Oxide layer)

Claims (3)

An oxide superconducting thin film provided on an oxide substrate;
An electrode comprising Au, Ag or an AgAu alloy provided on the oxide superconducting thin film;
A metal wire or an oxide superconducting wire connected to the oxide superconducting thin film;
A superconducting member comprising: a solder made of an InAg alloy with an addition amount of Ag of 0.5 wt% to 10 wt% connecting between the electrode and the wire. An oxide superconducting thin film provided on an oxide substrate;
An electrode provided on an oxide superconducting thin film, in which an Au layer and an Ag layer are stacked;
A metal wire or an oxide superconducting wire connected to the oxide superconducting thin film;
Superconducting member characterized by having solder Metropolitan composed of the electrode and for connecting between the wire, In or InAg alloy. The superconducting member according to claim 2, wherein the addition amount of Ag in the InAg alloy is 10 wt% or less.

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